The invention relates to a process for making aqueous hydrocarbon fuel compositions from a continuous process. More particularly, the invention relates to a continuous process for making an aqueous hydrocarbon fuel such as a diesel fuel or gasoline.
Internal combustion engines, especially diesel engines, using water mixed with fuel in the combustion chamber can produce lower NOx, hydrocarbon and particulate emissions per unit of power output. Nitrogen oxides are an environmental issue because they contribute to smog and pollution. Governmental regulation and environmental concerns have driven the need to reduce NOx emissions from engines.
Diesel fueled engines produce NOx due to the relatively high flame temperatures reached during combustion. The reduction of NOx production includes the use of catalytic converters, using xe2x80x9ccleanxe2x80x9d fuels, recirculation of exhaust and engine timing changes. These methods are typically expensive or complicated to be commercially used.
Water is inert toward combustion, but lowers the peak combustion temperature resulting in reduced particulates and NOx formation. When water is added to the fuel it forms an emulsion and these emulsions are generally unstable. Stable water-in-fuel emulsions of small particle size are difficult to reach and maintain. It would be advantageous to make a stable water-in-fuel emulsion that can be made continuously and stable in storage.
It would be advantageous to produce stable water-in-fuel emulsions by a continuous process because of increased throughput, increased shear efficiency, and cost effectiveness over a batch blending process. Applicant has discovered a continuous process to make stable water-in-fuel emulsions of small particle size.
The term xe2x80x9cNOxxe2x80x9d is used herein to refer to any of the nitrogen oxides, NO, NO2, N2O, or mixtures of two or more thereof. The terms xe2x80x9caqueous hydrocarbon fuel emulsionxe2x80x9d and xe2x80x9cwater fuel emulsionxe2x80x9d are interchangeable. The terms xe2x80x9caqueous hydrocarbon fuelxe2x80x9d and xe2x80x9cwater fuel blendxe2x80x9d are interchangeable.
The invention relates to a continuous process for making an aqueous hydrocarbon fuel, comprising: (1) mixing liquid hydrocarbon fuel and an emulsifier to form a hydrocarbon fuel/additive mixture; (2) emulsifying said hydrocarbon fuel/additive mixture with water under shear conditions to form an aqueous hydrocarbon fuel emulsion, wherein said emulsification is accomplished by at least two emulsifiers in series. The aqueous hydrocarbon fuel emulsion includes a discontinuous aqueous phase in a continuous fuel phase. The discontinuous aqueous phase comprises aqueous droplets having a mean diameter of 1.0 micron by the time the aqueous hydrocarbon fuel emulsion has been processed through the second emulsifier.
The water hydrocarbon fuel emulsion is comprised of water, fuel such as diesel, gasoline or the like and an emulsifier. The emulsifier includes but is not limited to: (i) at least one fuel-soluble product made by reacting at least one hydrocarbyl-substituted carboxylic acid acylating agent with ammonia or an amine, the hydrocarbyl substituent of said acylating agent having about 50 to about 500 carbon atoms; (ii) at least one of an ionic or a nonionic compound having a hydrophilic-lipophilic balance (HLB) of about 1 to about 40; (iii) a mixture of (i) and (ii); or (iv) a water-soluble compound selected from the group consisting of amine salts, ammonium salts, azide compounds, nitrate esters, nitramine, nitro compounds, alkali metal salts, alkaline earth metal salts, in combination with (i), (ii) or (iii).
The water hydrocarbon fuel emulsion optionally includes additives. The additives include but are not limited to a cetane improver(s), an organic solvent(s), an antifreeze agent(s), surfactant(s), other additives known for their use in fuels and combinations thereof.
This invention further provides for an apparatus for continuously making an aqueous hydrocarbon fuel, comprising: at least two emulsifiers in series; a tank containing a hydrocarbon fuel/additive mixture or separate tanks for the hydrocarbon fuel, emulsifier, additives, water, antifreeze or combinations thereof; pump(s) and conduit(s) for transferring the hydrocarbon fuel, additive, and/or emulsifier from the tanks to a first emulsification device; a conduit for transferring water from a water source to the first emulsification device; a conduit for transferring the aqueous hydrocarbon fuel emulsion from the first emulsification device to the second emulsification device; a conduit for transferring the aqueous hydrocarbon fuel emulsion from a second emulsification device to a fuel storage tank; a conduit for dispensing the aqueous hydrocarbon fuel emulsion from the fuel storage tank; a programmable logic controller for controlling: (i) the transfer of the components from the tanks to the first emulsification device (ii) the transfer of water from the water source to the first emulsification device; (iii) the emulsification of the hydrocarbon fuel/additive mixture and the water in the first emulsification device; (iv) the transfer of the aqueous hydrocarbon fuel emulsion from the first emulsification device to the second emulsification device; (v) the further emulsification of the hydrocarbon fuel emulsion in the second emulsification device, (vi) the transfer of the aqueous hydrocarbon fuel emulsions from the second emulsification device to a fuel storage tank; and (vii) a computer for controlling the programmable logic controller.
In one embodiment, the apparatus for the continuous process is in the form of a containerized equipment unit that operates automatically. This unit can be programmed and monitored locally at the site of its installation, or it can be programmed and monitored from a location remote from the site of its installation. The water fuel blend is dispensed to end users at the installation site. This provides a way to make the aqueous hydrocarbon fuel emulsions prepared in accordance with the invention available to end users in wide distribution networks.
As used herein, the terms xe2x80x9chydrocarbyl substituent,xe2x80x9d xe2x80x9chydrocarbyl group,xe2x80x9d xe2x80x9chydrocarbyl-substituted,xe2x80x9d xe2x80x9chydrocarbon group,xe2x80x9d and the like, are used to refer to a group having one or more carbon atoms directly attached to the remainder of a molecule and having a hydrocarbon or predominantly hydrocarbon character. Examples include:
(1) purely hydrocarbon groups, that is, aliphatic (e.g., alkyl, alkenyl or alkylene), and alicyclic (e.g., cycloalkyl, cycloalkenyl) groups, aromatic groups, and aromatic-, aliphatic-, and alicyclic-substituted aromatic groups, as well as cyclic groups wherein the ring is completed through another portion of the molecule (e.g., two substituents together forming an alicyclic group);
(2) substituted hydrocarbon groups, that is, hydrocarbon groups containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the group (e.g., halo, hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);
(3) hetero-substituted hydrocarbon groups, that is, hydrocarbon groups containing substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen and nitrogen. In general, no more than two, and in one embodiment no more than one, non-hydrocarbon substituent is present for every ten carbon atoms in the hydrocarbon group.
The term xe2x80x9clowerxe2x80x9d when used in conjunction with terms such as alkyl, alkenyl, and alkoxy, is intended to describe such groups that contain a total of up to 7 carbon atoms.
The term xe2x80x9cwater-solublexe2x80x9d refers to materials that are soluble in water to the extent of at least one gram per 100 milliliters of water at 25xc2x0 C.
The term xe2x80x9cfuel-solublexe2x80x9d refers to materials that are soluble in the fuel to the extent of at least one gram per 100 milliliters of fuel at 25xc2x0 C.
The term xe2x80x9cwater fuel emulsionxe2x80x9d is interchangeable with aqueous hydrocarbon fuel/additive emulsion.
The term xe2x80x9cwater fuel blendxe2x80x9d is interchangeable with aqueous hydrocarbon fuel.
The term xe2x80x9cfuel-chemical additives mixturesxe2x80x9d is interchangeable with hydrocarbon fuel/additive mixtures.
The Continuous Process
The invention provides for a continuous process for making an aqueous hydrocarbon fuel by forming a stable emulsion in which the water is suspended in a continuous phase of fuel wherein the water droplets have a mean diameter of 1.0 microns or less. The droplet size are in volume. The invention provides for in another embodiment an apparatus for continuously making the aqueous hydrocarbon fuel. The continuous process apparatus comprises at least two emulsification mixers in series, a tank(s) containing the hydrocarbon fuel, emulsifier, additives and combinations thereof, a tank containing the water, a product tank, pumps, conduits for transferring the fluids, and a programmable logic controller so that the process may be automatic.
In the practice of the present invention the aqueous hydrocarbon fuel is made by a continuous process capable of monitoring and adjusting the flow rates of the fuel, emulsifier, additives and/or water to form a stable emulsion with the desired water droplet size. The process and apparatus described below depict one embodiment of the continuous process. Referring to FIG. 1, the apparatus includes a fuel additive tank (10), a water feed tank (14), a product tank (18), a first emulsification device (22), a second emulsification device (26), and a fuel dispenser 30 (30). Initially the hydrocarbon fuel and the emulsifier are mixed in the fuel additives tank (10) to form a homogeneous hydrocarbon fuel/additives mixture. In another embodiment the feeds of the hydrocarbon fuel, the emulsifier and the additives are added to the water tank (10) by discreet feeds, or in the alternative combinations of the discreet feeds, to form a homogeneous hydrocarbon fuel/additive mixture. In another embodiment the emulsifier, the fuel and the additives are mixed dynamically and fed continuously and then processed with the water stream to form an aqueous hydrocarbon fuel emulsion.
The hydrocarbon fuel/additive mixture contains about 50% to about 99% by weight, in another embodiment about 85% to about 98% by weight, and in another embodiment about 95% to about 98% by weight hydrocarbon fuel, and it further contains about 0.05% to about 25%, in another embodiment about 2% to about 15%, and in another embodiment about 2% to about 5% by weight of the emulsifier.
Optionally, additives may be added to the emulsifier, the fuel, the water or combinations thereof. The additives include but are not limited to cetane improvers, organic solvents, antifreeze agents, surfactants, other additives known for their use in fuel and the like. The additives are added to the emulsifier, hydrocarbon fuel or the water prior to and in the alternative at the first emulsification device dependent upon the solubility of the additive. However, it is preferable to add the additives to the emulsifier to form an additive emulsifier mixture. The additives are generally in the range of about 1% to about 40% by weight, in another embodiment about 5% to about 30% by weight, and in another embodiment about 7% to about 25% by weight of the additive emulsifier mixture.
The hydrocarbon fuel/additives mixture stream exits the hydrocarbon fuel tank outlet (34) and flows through conduit (38) generally at a rate of about 0.5 gallon to 1000 gallons per minute, and in another embodiment about 10 gallons to about 600 gallons per minute into the first emulsification device (22) through conduit (38). The ratio of hydrocarbon fuel/additives mixture to water is in the range of about 50 to about 99 to about 50 to about 1, in another embodiment about 85 to about 95 to about 15 to about 5, in another embodiment about 75 to about 85 to about 25 to about 15, and in another embodiment about 70 to about 75 to about 30 to about 25.
The water, which can optionally include but is not limited to antifreeze, ammonium nitrate or mixtures thereof, flows out of water feed tank outlet (36) through conduit (46) into the first emulsification device (22) at a rate of 0.5 gallon to about 1000 gallons a minute, and in another embodiment about 10 gallons to about 600 gallons per minute. Ammonium nitrate is generally added to the water mixture as aqueous solution. In one embodiment the water, the alcohol and/or the ammonium nitrate are mixed dynamically and fed continuously to the fuel additives stream. In another embodiment the water, antifreeze, ammonium nitrate or mixtures thereof flow out of separate tanks and/or combinations thereof into or mixed prior to the first emulsification device (22). In one embodiment the water, water alcohol, water-ammonium-nitrate, or water-alcohol ammonium nitrate mixture meets the hydrocarbon fuel additives mixture immediately prior to or in the first emulsification device (22).
The hydrocarbon fuel additive stream during startup and shutdown is such that the ratio of water to hydrocarbon fuel additive is never greater than the steady state condition.
In one embodiment arranged in series between the fuel additive tank (10) and the first emulsification device (22) are a feed pump (42), a flow meter (44), a shut-off valve (46), a check valve (48), a temperature gauge (50), and a pressure gauge (52). In one embodiment arranged in series between the water tank (14) and the first emulsification device are a valve (54), an aqueous feed pump (56), a flow meter (58), a shut-off valve (60), and a check valve (62).
The first shearing is generally in the first emulsification device (22) and processed generally under ambient conditions. The first emulsification occurs generally with a pressure drop in the range of about 0 psi to about 10 psi, in another embodiment in the range of about 10 psi to about 80 psi, and in another embodiment in the range of about 15 psi to about 30 psi.
The first emulsification device (22) is used to thoroughly mix the components to produce a more uniform dispersion of the water droplets in the fuel, as well as to impart some of the shearing needed to reduce the water droplet size so that the second emulsification device provides the desired water droplet size. This step distributes the concentration of the components more uniformly through the mixture. The first emulsification device (22) is also used to insure that the additives have good contact with the aqueous components before being fed to the second emulsification mixer (26). The emulsion is mixed in the first emulsification device (22) until an emulsion has proceeded to having a mean droplet particle size of greater than 1 micron, in another embodiment about 1 micron to about 1000 microns, and in another embodiment about 50 microns to about 100 microns, and in another embodiment about 1 micron to about 20 microns.
The first emulsification occurs by any method used in the industry including but not limited to mixing, mechanical mixer agitation, static mixers, shear mixers, sonic mixers, high-pressure homogenizers, and the like. Examples of the first emulsification devices include but are not limited to an Aquashear, pipeline static mixers and the like. The Aquashear is a low-pressure hydraulic shear device. The material is forced through two facing plates with drilled holes into the mixing chamber. The two plates cause counter rotational flow and allow the material to mix. The Aquashear mixers are available from Flow Process Technologies Inc.
The emulsion then flows out of the first emulsification device outlet (64) through conduit (68) directly to the second emulsification device (26). There is no intermediate holding tank between the first emulsification device (22) and the second emulsification device (26). Arranged in series along conduit (68) between the first emulsification device (22) and the second emulsification device (26) is a temperature gauge (70), a pressure gauge (72), a valve (80), and a flow meter (82). The emulsion stream flows directly from the first emulsification device (22) to the second emulsification device (26). There is no holding tank between the first emulsification device (22) and the second emulsification device (26). The emulsion is not aged between the first emulsification device (22) and the second emulsification device (26). Generally the time the emulsion flows from the first emulsification device (22) to the second emulsification device (26) in less than 5 minutes, in another embodiment less than 4 minutes, in another embodiment less than 3 minutes, in another embodiment less than 2 minutes, in another embodiment less than 1 minute, and in another embodiment less than 30 seconds.
The second emulsification is a high-shear device and occurs under ambient conditions. The second emulsification device (26) results in emulsion having a mean particle droplet size in the range of about 0.01 micron to about 1 micron, in one embodiment in the range of about 0.1 micron to about 0.95 microns, in one embodiment in the range of about 0.1 microns to about 0.8 microns and in one embodiment in the range of about 0.1 microns to about 0.7 microns. A critical feature of the invention is that the water phase of the aqueous fuel product is comprised of water droplets having a mean diameter of one micron or less. Thus the second emulsification is conducted under sufficient conditions to provide such a mean droplet particle size.
High-shear devices that may be used include but are not limited to IKA Work Dispax, the IK shear mixers include the DR3-6 with three stages of rotor/stator combinations. The tip speed of the rotor/stator generators may be varied by a variable frequency drive that controls the motor. The Silverson mixer is a two-stage mixer, which incorporates a rotor/stator design. The mixer has high-volume pumping characteristics similar to centrifugal pump. Inline shear mixers by Silverson Corporation (a rotor-stator emulsification approach); Jet Mixers (venturi-style/cavitation shear mixers), Ultrasonolator made by the Sonic Corp. (ultrasonic emulsification approach), Microfluidizer shear mixers available by Microfluidics Inc. (high-pressure homogenization shear mixers), ultrasonic mixers, and any other available high-shear mixer.
There can be one or more emulsification devices used in series and used for final shearing size. These emulsification devices have to have the ability to reduce the mean particles size of the water droplet to less than one micron. By using at least two emulsification devices in series, more shear is directed to the emulsion. This decreases the overall particle size and increases emulsion stability. The mixers described for the first emulsification device and for the second emulsification device are generally interchangeable, however, the second emulsification device needs to be a high shear device.
The emulsion then flows out of the second emulsification device outlet (84) through conduit (86) to the product tank (18). Arranged in series along a conduit (86) are a sampling valve (88), a temperature gauge (90), a pressure gauge (92), and a check valve (94).
The continuous process is generally processed under ambient conditions. The continuous process is generally done at atmospheric pressure. The continuous process generally occurs at ambient temperature. In one embodiment the temperature is in the range of about ambient temperature to about 212xc2x0 F., and in another embodiment in the range of about 40xc2x0 F. to about 150xc2x0 F.
A programmable logic controller (plc), not shown in FIG. 1, is provided for governing the continuous flow of the aqueous hydrocarbon fuel additive mixture, the water, and aqueous hydrocarbon fuel emulsion thereby controlling the flow rates and mixing ratio in accordance with the prescribed blending rates. The plc stores component percentages input by the operator. The plc then uses these percentages to define volumes/flow of each component required. Continuous flow sequence is programmed into the plc. The plc electronically monitors all level switches, valve positions and fluid meters.